Hurricane Joaquin moved slowly through the eastern Bahamas on 1 and 2 October 2015. ASCAT data from 1356 UTC, above, shows rain-flagged values near 90 knots not far from the storm center (Joaquin is a potent Category 4 Hurricane; its strongest winds are confined to within about 50 miles of the center).

MIMIC Total Precipitable Water for the 72 hours ending 1900 UTC on 2 October [click to enlarge]

Joaquin is embedded within a very moisture-rich environment, and that tropical moisture will move inland over the Carolinas and surrounding states over the weekend and produce heavy rains. The animation of MIMIC Total Precipitable Water, above, shows a corridor of very high total precipitable water just offshore of the Carolinas at the end of the animation, ready to shift inland.